When selecting a cosmetic it is extremely important to precisely determine the condition of the skin, and in order to maintain a more desirable skin condition it is necessary to select cosmetics and cosmetic methods suited for the particular skin condition. Evaluation of skin condition is carried out by measuring skin softness using a Reviscometer or Cutometer, by measurement of transepidermal water loss (TEWL), by measurement of skin physiology with a microscope, or by evaluation of the stratum corneum using a tape strip (NPLs 1, 2 and 3, and PTL 1). Of these, evaluation of the stratum corneum using a tape strip allows easy sampling and is considered effective for properly evaluating skin condition, and a method has been disclosed in which observation of the shapes, area and presence of nuclei in the cornified cells is also combined with observation of the stratum corneum stained with congo red that is capable of staining the β-sheet structure, to allow diagnosis of the softness of the skin (PTL 2).
Skin softness represented by the abundance of the β-sheet structure is one indicator of the stratum corneum condition, but in addition to softness, other various properties such as transparency, stratum corneum intercellular lipid structure and stratum corneum barrier function also indicate the stratum corneum condition. However, insufficient research has been conducted toward convenient measurement of such information based on tape-stripped stratum corneum, and no method has been established to allow convenient diagnosis of skin roughened state.